1. Field of the Invention
The present invention relates to a supercharging structure for a fan, wherein the thickness of the casing of the fan can be varied in response to a change in the height of the fan wheel while providing an airflow driven by the axial flow fan with a relatively high blast pressure on the air outlet side.
2. Description of the Related Art
U.S. Pat. No. 6,244,818 to Chang issued on Jun. 12, 2001 discloses a fan guard structure for additional supercharging function. As illustrated in FIG. 1 of the drawings that corresponds to FIG. 2A of U.S. Pat. No. 6,244,818, the fan guard 90 comprises a motor holder 91 and plural radial guard blades 92. A rotor device is mounted to the motor holder 91 and comprises a motor 93 for driving a shaft ring (fan wheel) 94. When the fan wheel 94 turns, surrounding air is introduced by the rotor blades 95 to generate an airflow which is outputted after passing through gaps between the guard blades 92. The blast pressure is changed from a relatively low value on the air inlet side into a relatively high value on the air outlet side. That is, there is a blast pressure enhancement on the air outlet side.
As illustrated in FIG. 2 that corresponds to FIG. 7 of U.S. Pat. No. 6,244,818, a composite fan comprises two fan units 90 each including guard blades 92 and the rotor device mentioned above, which also fulfills the function of improving performance of the fan.
The fan disclosed in U.S. Pat. No. 6,244,818 has a fixed thickness (or height), as the thickness of the casing 90 and of the fan wheel 94 is fixed. Thus, factories manufacturing the fans must prepare molds for manufacturing casings 90 of various thicknesses. In addition, spare products are required for different needs.
Furthermore, mounting of the motor 93, fan wheel 94, and drive circuit of the rotor device into the casing 90 becomes difficult when the casing 90 is relatively thick. Further, inconvenience was found when mounting the fan disclosed in U.S. Pat. No. 6,244,818 on a heat-dissipating member, which is the most common use of the fan.
It is, therefore, an object of the present invention to provide a supercharging structure for a fan, wherein the thickness of the casing of the fan can be varied in response to a change in the fan wheel.
Another object of the present invention is to provide a supercharging structure for a fan, wherein the rotor device of the fan can be assembled easily.
A further object of the present invention is to provide a supercharging structure for a fan, wherein the fan can be directly engaged with a heat-dissipating member to thereby form a heat-dissipating unit.
A fan having a supercharging structure comprises a casing having an air passage hole with an air inlet at a first end thereof and an air outlet at a second end thereof. A base is mounted to the air outlet end of the casing. A supporting plate is mounted in the air passage hole of the casing or in an air outlet in the base for engaging with a stator bobbin that pivotally holds a fan wheel to be driven. Plural supercharging plates are mounted between the supporting plate and the base.
Other objects, specific advantages, and novel features of the invention will become more apparent from the following detailed description and preferable embodiments when taken in conjunction with the accompanying drawings.